Coded thin layer chromatography support

ABSTRACT

Support materials for thin-layer chromatography characterized by a marker code applied using laser light.

The invention relates to a coded support for thin layer chromatography("TLC") and to a process for its production.

The developments on modern analysis methods are ever increasing, forexample with regard to accuracy, reproducibility, unambiguous assignmentand documentation of analysis results. Thus, the increasing demands fordocumentation have been met, for example, in guidelines such as DIN-ISO9000, Good Manufacturing Practice (GMP) or Good Laboratory Practice(GLP).

It is correspondingly necessary to individually mark or code evenready-prepared layers in TLC during and after their chromatographic use,and therefore make them impossible to mistake for each other.

Such a marking should have the highest possible information density andbe capable of being applied quickly onto or into the respective layer.Above all, however, it should be resistant to all organic and inorganicsolvents, bases and acids (not only in liquid form, but also in the caseof gas-phase action as a result of vaporization) which areconventionally used in TLC so that neither the chromatographicdevelopment nor the result of the separation is disrupted or affected.In addition, the marking should be readable not only in daylight butalso under UV illumination (for example 254 and 366 nm).

The markings conventionally used to date, for example by sticking onlabels or inscriptions in the carrier layer, satisfy these requirementsonly partially or not at all, and are also laborious. As a result ofmanual data transfer, transfer errors can make the entries unusable.Labels can become detached and be lost.

The object of the invention was to provide marked (coded) TLC supportswhich present the specified disadvantages not at all or only to a lesserextent.

It was surprisingly found that the intended result can be achieved byexposing the support to laser light, a corresponding template being used(for example numbers and/or letters or else lines for bar coding) or thelaser being controlled by means of a computer. This produces a permanentmark which is easy to read in daylight and under UV light. When thelaser is controlled by means of a computer, no templates are required.

The subject of the invention is correspondingly a TLC supportcharacterized by a coding applied by means of laser light, and a processfor its production, characterized in that a conventional TLC support isexposed to laser light.

Supports are primarily glass plates and foils (for example aluminumfoils or plastic films, for example those made of polyterephthalate),which are coated with sorbent and contain a binder as well as,optionally, a fluorescent indicator and/or further additives.

All stationary phases conventionally used in TLC are suitable assorbents, preferably modified or unmodified silica gels, as well as, forexample, celluloses, polyamides, diatomaceous earth, aluminum oxides.

Polymeric organic substances are preferably used as binders, for examplepolyacrylic acid or polymethacrylic acid, and amides thereof.

A pulsed or continuous CO₂ laser (wavelength 1.06 μm) or a Yag laser(solid-state laser, wavelength 10.6 μm) is preferably used as the lasersource. The exposure time is typically equal to 5-50 nanoseconds persymbol.

The coding obtained may contain any data, for example logo of theproducer company, item number, batch number, date of production, uniqueindividual numbering (serial numbering).

Coding is preferably carried out by exposing the sorbent layer, whichcontains a binder. It is, however, also possible to make a laserinscription on the uncoated back of a support glass plate or a coatedplastic film. In the case of a glass plate, the exposure produces finethermal stress cracks which causes opaqueness of the glass surface thatcan be discerned in the visible light wavelength range.

Even without further comments, it will be assumed that a person skilledin the art can use the above description in the widest scope. Thepreferred exemplary embodiments should therefore be taken merely by wayof description, without any limitation being implied.

The full disclosure of all applications, patents and publicationsreferred to above and below, and of the corresponding application DE 4330 564, filed on 09 Sep. 1993, are included in this application byreference.

EXAMPLES Example 1

A ready-prepared HPTLC plate (E. Merck silica gel 60 F₂₅₄, item No.5642, 100×200 mm) is exposed to a pulsed CO₂ laser, wavelength 10.6 μm,exposure time respectively 50 nanoseconds for each individual symbol. Inthis case a mask is used, which covers most of the plate, except for theopenings for the desired symbols; the plate being moved in such a waythat each individual exposure is incident at the point for therespectively desired symbol.

Example 2

A ready-prepared HPTLC plate (E. Merck silica gel 60, item No. 5641,100×200 mm) is inscribed on using a continuous CO₂ laser (wavelength10.6 μm, power consumption 10 watts, speed of advance 100 mm/sec). Inthis case the laser is controlled using a computer.

We claim:
 1. A coded thin layer chromatography material which comprisesa support coated with a sorbent layer consisting essentially of sorbentparticles and a binder wherein the sorbent layer has an alphanumericidentifier or a bar coding thereon formed by a process consistingessentially of exposing the sorbent layer to laser light in analphanumeric or bar coding pattern such that the coding is readable ineither visible or ultraviolet light.
 2. The thin layer chromatographysupport of claim 1, wherein the support comprises a glass plate, foil orplastic film.
 3. The thin layer chromatography support claim 1, whereinthe sorbent particles are of modified or unmodified silica gel,cellulose, polyamide, diatomaceous earth or aluminum oxide material. 4.The thin layer chromatography support of claim 1, wherein the sorbentparticles are of modified or unmodified silica gel material.
 5. The thinlayer chromatography support of claim 1, wherein the binder is apolyacrylic acid, polymethacrylic acid or an amide thereof.
 6. A processfor coding a thin layer chromatography material comprising a supporthaving a sorbent layer thereon consistng essentially of sorbentparticles and a binder, which process consists essentially of exposingthe sorbent layer to laser light in an alphanumeric or bar codingpattern to produce an alphanumeric or bar coding thereon which isreadable in either visible or ultraviolet light.
 7. The process of claim6, wherein the laser light is from a pulsed or continuous CO₂ laser orYag laser.
 8. The process of claim 6, wherein the exposure time of thelaser light is 5 to 50 nanoseconds per coding symbol.
 9. The process ofclaim 6, wherein the laser light is directed by computer to apply thecoding.